The present invention relates to a shroud for a steel making arc furnace and more particularly relates to a shroud which can prevent the diffusion of exhaust gas, dust and the like through a cable hole on the top of the shroud into the atmosphere.
In order to minimize the diffusion and discharge into the surrounding atmosphere of dust, exhaust gas and the like during the operation of an arc furnace, the arc furnaces are in general surrounded by a shroud comprising dust proof side walls and a dust proof top wall.
Referring to FIG. 1, a conventional shroud will be described. A shroud 2 surrounding an arc furnace main body 1 has a dust collector 3 disposed at the undersurface of a top wall 7, an opening in a side wall 4 for lateral movement of a scrap bucket 5 into or out of the shroud 2, doors 6 adapted to close said opening, a further opening 9 on the top wall 7 for passage of a bucket suspending cable 8, a panel 10 for opening or closing the opening 9, and an air curtain device 12 disposed adjacent to the opening 9. When scrap metal 13 is charged into the arc furnace, the air curtain device 12 is driven so that the exhaust gas (indicated by the arrow a) from the arc furnace main body 1 is sucked as indicated by the arrow b and then discharged in the direction as indicated by the arrow c along an inclined flange 14, whereby the exhaust gas flows into a suction port 15 of the dust collector 3.
Referring next to FIGS. 2 and 3, another conventional shroud will be described. The top wall 7 of the shroud 2 is formed with a suction port 16 which is communicated with a dust collector (not shown). Two semi-portal doors 17 for covering a scrap bucket opening are adapted to move sideward along the shroud to the positions indicated by the imaginary lines. A small opening 18 allowing to pass a bucket-suspension cable (not shown) when the doors 17 are closed is formed at the tops of the doors 17. An air curtain device 19 is disposed for discharging air in the direction as indicated by the arrow d so as to seal the opening 18.
In the above-described conventional shroud, the air curtain devices 12 and 19 are of the pusher type so that the openings 9 and 18 are not satisfactorily sealed. Especially in the case of the shroud shown in FIG. 1, the distance between the discharge port of the air curtain device 12 and the suction port 15 of the dust collector 3 is so long that it becomes difficult to process a large quantity of exhaust gas discharged when scrap metal is charged into the furnace. As a result, part of the exhaust gas leaks through the opening 9 into the surrounding atmosphere. Furthermore, the air curtain device 12 is disposed within the shroud 2 so that it is exposed to the high temperature atmosphere containing dust. As a result, there is a defect that a motor and a fan of the air curtain device 12 are damaged. In the case of the shroud of the type described with reference to FIGS. 2 and 3, there is a defect in that the air for forming an air curtain is wasted. Primarily, the air curtain should operate only for several minutes during which the crap metal is charged. But, the air curtain device 19 must be driven constantly so as to seal the opening 18, resulting in increased consumed air volume.